1. Field of the Invention
The present invention relates generally to methods and apparatus for displaying a selected portion of a graphical image in a window on a monitor and more particularly to methods and apparatus in which a scroll box on one side of the window is provided for changing the displayed portion of the image responsive to movement of the scroll box.
2. Description of the Related Art
Scroll boxes are commonly used for locating and displaying a portion of a file in windowing programs such as Microsoft Windows.TM. and MOTIF.TM.. A scroll bar indicates the possible areas to be viewed and a scroll box position on the scroll bar indicates the position of that portion of the file in the window relative to the total file length. For example, in a word processing program if the scroll box is halfway down the scroll bar it indicates that the screen is displaying a portion from approximately the middle of the document. In some such programs, the size of the scroll box changes relative to the scroll bar to indicate a percentage of the displayed portion of the image relative to the entire image. In other words, the scroll bar is proportional to the length of the entire image and the scroll box is proportional to the length of the displayed image.
In such a system an operator uses a mouse to position the cursor on the scroll box, depresses a button on the mouse, and moves the mouse thereby moving the scroll box so long as the mouse button is depressed. Such mouse movement moves the box relative to the scroll bar. When the mouse button is released a new portion of the file corresponding to the new scroll box position is displayed in the window.
Often, graphical images, such as data in the form of graphs are displayed in a window formed on a monitor by a computer. For example, a patient may be fitted with an heart rate recorder which records heart rate waveforms generated by the patient for predetermined period of time. Typically the time period is 24 hours. The recorded data is played back and stored in the computer memory for display in a window formed on a monitor as described above.
Such a graph must be manipulated in order to change the scale, e.g., "to zoom in" to a particular portion of the graph to reveal details or to "zoom out" to observe an overall pattern. The scale of the graph and the portion being viewed are independent parameters. By analogy, if the graph were printed on paper, a magnifying glass could be positioned over the paper. The height of the magnifying glass controls the magnification while the lateral and longitudinal positions of the glass determine which portion of the graph is viewed. When a graph is displayed on a computer monitor, separate controls are used to select a portion of the graph for viewing and to select the scale of the viewed portion.
It would be desirable to provide an integrated control for selecting a portion of the graphical image for viewing and for selecting the scale of the viewed portion.